Composite electrical conductor



Sept. 26, 1944. p. D JR 2,359,090-

COMPOSITE ELECTRICAL CONDUCTOR Filed April 16, 1943 HIGH TENS/LE .STEENG TH [N1 'EN TOR: DAN/EL P Org/e, J/a,

Patented Sept. 26, 1944 2,359,090 coMPosrrn ELECTRICAL CONDUCTOR Daniel P. Dyer,

Jr., Chagrin Falls, Ohio, assignor to The American Steel and Wire Company of New Jersey, a

corporation of New Jersey Application April 16, 1943, Serial na isazse 3 Claims. (01.174-428),

This invention relates to overhead electric transmission linesjespecially of the type now being commonly used in carrying out rural electrification projects, and particularly to an improved composite electrical conductor therefor.

This application is 'a continuation-impart of my copending application, Serial No. 348,477, filed July 30, 1940, which has matured to Patent No. 2,321,021 dated June 8, 1943.

It is well known that rural electric transmission lines are characterized by the use of poles which are spaced greaterdistances than is normally considered good practice. Economy dictates that these poles be relatively short, it following that the conductors must be strung under relatively high tension to prevent them sagging an excessive amount. Economy also dictates that the conductors be of a relatively inexpensive construction.

A single wire conductor isof such a shape that the wind gives rise to excessive transverse vibration which so stresses the conductor as to cause its premature fracture through fatigue. Two intertwisted wires, through some form of propeller action in the wind, result in torsional vibration, this resulting in the premature failure of this type of a conductor also through fatigue.

A conductor consisting of three intertwisted wires has substantially a triangular cross section, and it has been found that a conductor having such a cross section is less subject to the action.

of the wind than conductors having other forms of cross sections. Also, a conductor strand made of three intertwisted wires is not particularly subject to either transverse or torsional vibration, although it still has some tendency to vibrate either transversely or torslonally. It'is for these reasons that the three-wire conductor strand is generally used for rural electrification purposes. i

Because of electrical reasons, as is well known to those skilled in the art, these threewire conductor strands are made with one or two of the wires of copper and with the remainder of the wires made of steel or some other suitable highstrength material, or with one or two of the wires oi. low carbon steel and with the remainder of the wires of high carbon steel and usually with all of the wires having the samediameter.

However, an electricalconductor consisting of three intertwisted wires, as above described, is unsatisfactory for long spans for the reason that there is too great a degree of elongation in the conductor, thereby resulting in an excessive sag between the poles or points of support. That is,

the amount of steel contained in the steel wire of the same diameter as the copper wires does not provide suiilcient overall tensile strength in the conductor.

Since, for reasons of good practice, it has been found undesirable to increase the tensile strength f the steel in the steel wire, the only alternative remaining was to increase its diameter and maintain the original diameter of the copper wires, but if the creased, in such an intertwisted construction, it has been found that while the tensile strength of the construction was increased materially, it

sion in the conductor thereby reducing the num-,

ber of poles or points of support per mile to a minimum and a consequent reduction in the cost of such lines.

Accordingly, it is one of the objects of the present invention to provide an improved composite electrical conductor for overhead transmission lines which is simple and inexpensive in its construction and use, and one which not only posseses the high tensile strength necessarily requiredof such a conductor, but all the other characteristics required of a good electrical c'onductor.

It is another object of the invention to provide an improved composite electrical conductor which is strong and rugged and one which requires less material per unit of length in its construction than any conductor heretofore suggested or used so as to provide a high-strength low-weight ratio conductor and, at the same time, a conductor which has a minimum amount of sag or elongation per unit of length. Y Various other objects and advantages of this invention will be more apparent in the course 01' the following specification and will be particularly pointed out in the appended claims.

In the accompanying drawing there is shown, for the purpose of illustration, one embodiment which my invention may assume in practice.

In the drawing:

Figure 1 is a plan view of 'a portion ofthe imsize of the steel wire is 111-,

proved composite electrical conductor of my in= vention; and

Figure 2 is a cross section thereof.

Referring more particularly to the drawing, the improved composite electrical conductor of my invention comprises preferably a galvanized relatively straight steel or steel alloy wire 2 having a relatively high tensile strength or a wire made from some other suitable high tensile strength material such as bronze, high-strength aluminum, aluminum alloy, brass, chrome, chromenickel, and th like, which is adapted to form a core. There is helically wound or twisted around the steel wire core 2 in side by side relation, preferably a pair of galvanized copper wires 3 or wires made of other suitable metal having the quality of good electrical conductivity such as aluminum, manganese, iron, zinc, and the like. In other words, the steel or high tensile strength wire 2 is substantially straight and acts as a core for the two copper or other good conductor wires 3 which are wrapped therearound. It will be understood that the two copper wires 3, preferably, are not preformed but are merely stranded together about the steel wire core 2. In some instances, and for certain uses, it may be desirable that the wire core 2 and the outer wires 3 be.

of thesa ne material.

The steel or high tensile strength wire core 2 has a diameter, preferably, of from approximately .086 to .243 of an inch, and the diameter of each of the copper or wires of good electrical conductivity t has a diameter, preferably, of from approximately .072 to .182 of an inch. Within these ranges, the cross-sectional area of the high tensile strength wire should be approximately from 0.7 to 0.9 of the combined cross-sectional area of the pair of copper or wires of good electrical conductivity in order to-provide a satisfactory conductor. That is to say, the minimum cross-sectional area of the steel wire 2 in any particular case would be 0.7 of the combined cross-sectional areas of the two copper wires 3 with 0.8 of the combined cross-sectional areas of the copper wires being the ideal, and 0.9 'of the combined cross-sectional areas of the two copper wires being the maximum size of the steel wire. It has been found that a steel wire having a diameter of approximately .112 to .115 of an inch, with .copper wires each having a diameter of approximately .093 of an inch, provides a conductor practical for most uses.

Also, according to the present invention, it has been found that the length of pitch, between the helices of the pair of copper wires 3, as designated at P in Figure 1 of the drawing, should b approximately from twelve to eighteen times the overall or effective strand. It will eunderstood that the overall or effective diameter as above referred to means the diameter of a circle circumscribing the three wires, namely, the steel wires 2 and two copper wires 3.in their assembled position. Thus, it will be seen, for example, that in using a steel wire having a diameter of .115 of an inch with the copper wires each having a diameter of .093 of andnch, the length of pitch Por lay of the pair of: copper wires is twelve to eighteen times the overall or effective diameter of .208 of an inch, which equals approximately .two and one-half to four inches. In other words, the pitch or lay of the pair of wires 3 example, is between'two and one-half and four inches *so'as to provide a satisfactory conductor in diameter of the conductor or accordance with the teachings and principles of my invention.

It is preferable that the steel wire 2 have an elongation of approximately from'iive to six percent and with the copper wires 3 having a maximum elongation of approximately one and onehalf percent. The reason for this is to permit the full strength of the steel wire to absorb any stress to which the conductor is subjected before any material amount of stress is transmitted to the copper wires and causes premature failure thereof. As will be readily seen, such a result is obtained from the manner in which the pair of copper wires is shaped or wound around the steel wire core. That is, the copper wires so arranged will tend to be deformed about the steel wire before being subjected to any excessive strain.

Thus, it will be, seen that when the conductor is under stress, the steel wire will stretch and reach' the limit of its five to six percent elongation at about the same time that the copper wires are beginning to reach the limit of their one and one-half percent elongation, and the result would be that'this construction favors the elongation limitations of the high drawn copper wires. It will be understood that in a three-wire conductor strand made of copper and steel wires of the conventional inter-twisted type as heretofore used, such a result will not be obtained for the reason that when the conductor was under stress, the copper wires were usually under such stress that they broke before the steel wire, with its extra elongation, had a chance to carry its share of the load up to its full capacity.

As a result of my invention, it will be seen that the steel wire of the composite conductor acts entirely as a structural member and the copper wires act entirely as electrical conductors. It will also be seen that in the conductor of the present invention, all of the advantages of a single straight steel wire conductor are obtained, and

yet, at the same time, the cross section of the 1 present conductor at any point in triangular as shown in Figure 2 of the drawing, thereby obtaining all those advantages of a three-wire conductor. It will be seen further that my improved conductor, due to its construction, can be strung with longer spans for the same amount of sag about the steel wire 2, in this with any given tension than any three-wire conductor heretofore proposed or used.

While I have shown and described an embodiment of my invention, it will be understood that I do not wish to be limited exactly thereto, since various modifications may be made without departing from the scope of the invention, as defined in the appended claims.

I claim:

1. As a new article of manufacture, a composite electrical conductor consisting of three wires with one of said wires being a relatively straight wire having a relatively high tensile Y strength which is adapted to form a core and having a diameter of approximately from .086 to .243 of an inch, and with the other of said wires consisting of a pair of wires each having a diameter of approximately from .072 to .182 of an inch having the qualities of good electrical conductivity helically woundaround said high tensile strength wire in side by side relation with said'high tensile strength wire having a cross-sectional area of approximately from 0.7 to 0.9 of the combined crosssectional areas of both of said wires of good electrical conductivity.

2. As a new article of manufacture, a composite electrical conductor, as defined in claim 1,

wherein the wire of relatively high tensile strength consists of steel and each of vthe pair of wires of good electrical conductivity consist of copper.

3. As a new article of manufacture, a composite electrical conductor consisting of three wires with one of said wires being a relatively straight wire having a relatively high tensile strength which is adapted to form a core and having a diameter of approximately from .086 to .243

having the qualities of good electrical conductivity helically wound around said high tensile strength wire in side by side relation with said high tensile strength wire having a cross-sectional area of approximately from 0.7 to 0.9 of the combined crosssectional areas of both of said wires of good electrical conductivity, and with the pitch of the helices of said helically wound wires being approximately from twelve to eighteen times the overall diameter of the completed conductor.

DANIEL P. DYER, JR.

of approximately from .072 to .182 of an inch x 

